PIX 515 UR (7.23) vs. SNAF & SNAA

Guys,

I recently found a PIX 515E unrestricted with max RAM running 7.23 and the ASDM 5. Is this worth using or should I just jump up to an ASA 5505 (or two?) and not waste my time?

I know the older PIXes don't run the newer versions...

Thanks,
HT